#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
int main()
{
  pid_t pid;
  printf("Before: pid is %d\n",getpid());
  if((pid=fork())==-1) 
  {
    perror("fork()");
    exit(1);
  }
  printf("After: pid is %d ,fork() return %d\n",getpid(),pid);
  sleep(1);
  return 0;
}
